Remove use of deprecated MessageLoop methods in chrome/.

chrome/browser/chromeos/policy/device_system_use_24hour_clock_browsertest.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/shell.h"
 #include "ash/system/date/date_default_view.h"
 #include "ash/system/date/date_view.h"
 #include "ash/system/user/login_status.h"
 #include "base/command_line.h"
+#include "base/location.h"
 #include "base/macros.h"
 #include "base/message_loop/message_loop.h"
+#include "base/single_thread_task_runner.h"
+#include "base/threading/thread_task_runner_handle.h"
 #include "chrome/browser/chromeos/login/ui/login_display_host.h"
 #include "chrome/browser/chromeos/policy/device_policy_cros_browser_test.h"
 #include "chrome/browser/chromeos/policy/proto/chrome_device_policy.pb.h"
 #include "chrome/browser/chromeos/settings/cros_settings.h"
 #include "chrome/browser/lifetime/application_lifetime.h"
 #include "chrome/browser/ui/ash/system_tray_delegate_chromeos.h"
 #include "chromeos/chromeos_switches.h"
 #include "content/public/test/test_utils.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ skipping 14 matching lines @@
 
   void SetUpInProcessBrowserTestFixture() override {
     InstallOwnerKey();
     MarkAsEnterpriseOwned();
     DevicePolicyCrosBrowserTest::SetUpInProcessBrowserTestFixture();
   }
 
   void TearDownOnMainThread() override {
     // If the login display is still showing, exit gracefully.
     if (LoginDisplayHost::default_host()) {
-      base::MessageLoop::current()->PostTask(FROM_HERE,
-                                             base::Bind(&chrome::AttemptExit));
+      base::ThreadTaskRunnerHandle::Get()->PostTask(
+          FROM_HERE, base::Bind(&chrome::AttemptExit));
       content::RunMessageLoop();
     }
   }
 
  protected:
   void RefreshPolicyAndWaitDeviceSettingsUpdated() {
     std::unique_ptr<CrosSettings::ObserverSubscription> observer =
         CrosSettings::Get()->AddSettingsObserver(
             kSystemUse24HourClock,
             base::MessageLoop::current()->QuitWhenIdleClosure());
@@ skipping 106 matching lines @@
   EXPECT_TRUE(CrosSettings::Get()->GetBoolean(kSystemUse24HourClock,
                                               &system_use_24hour_clock));
   EXPECT_FALSE(system_use_24hour_clock);
   EXPECT_FALSE(GetSystemTrayDelegateShouldUse24HourClock());
   EXPECT_EQ(base::k12HourClock, TestGetPrimarySystemTrayTimeHourType());
   EXPECT_TRUE(TestPrimarySystemTrayHasDateDefaultView());
   EXPECT_EQ(base::k12HourClock, TestGetPrimarySystemTrayDateHourType());
 }
 
 }  // namespace chromeos